In the commercial production of polymers and copolymers of vinyl and vinylidene halides, when polymerized alone or with other vinylidene monomers having a terminal CH.sub.2 .dbd.C&lt; group, or with polymerizable polyolefinic monomers, the buildup of polymer on the internal surfaces of the reactor is not only troublesome but costly. For example, when polymerizing vinyl chloride, and other comonomers when used, the same are maintained in the form of discrete droplets in an aqueous suspension by the use of suspending agents and agitation. When the reaction is complete, the resultant polymer, or PVC, is washed and dried. However, these suspension systems are often not as stable as they should be and during the polymerization reaction, vinyl chloride polymer builds up on the interior surfaces of the reactor, including the surfaces of the baffles and agitator. Obviously, this polymer buildup must be removed since it results in further formation of polymer buildup which in turn results in a crust that adversely affects heat transfer and contaminates the polymer being produced. While various methods have heretofore been proposed to reduce the amount and nature of polymer buildup on polymerization reactor surfaces, such as solvent cleaning, various hydraulic and mechanical reactor cleaners, and the like, none has proved to be the ultimate in polymer buildup removal. That is to say, these various methods and apparatus have done an acceptable job but there is still room for improvement in this area, particularly from an economic point of view.
Various methods have been proposed to prevent, or substantially eliminate, the formation of the polymer buildup in the first instance. For example, it has been proposed to coat the internal surfaces of the reactor with various polymer buildup resistant coating materials. For example, in U.S. Pat. Nos. 4,024,330 and 4,024,301, various polyaromatic amines are shown as useful for coating reactors to substantially eliminate buildup. Alkali soluble dyes have been shown to be useful for this purpose in U.S. Pat. No. 4,068,059. Further, in U.S. Pat. No. 4,080,173 there is shown and described the use of selfcondensed polyhyd2ric phenols and polyhydric naphthols as useful coating materials to prevent polymer buildup. While all these coating materials give good to excellent results, the search continues for new and improved polymer buildup resistant materials with which to coat reactors for the purpose of preventing or eliminating polymer buildup on the inner surfaces thereof.
Further, a recently published Japanese patent application discloses an interesting coating for polymerization reactors. This is Japanese patent application No. 127682/78, filed Oct. 17, 1978 in the name of Kanegafuchi Chem. K.K. and published Apr. 21, 1980 under Laid-open Gazette No. 55-054317. In this case the reactor is coated with the reaction product of pyrogallol or hydroxyhydroquinone alone, or other phenolic compounds containing either or both of them, with aromatic aldehydes. The reaction products are the acidic form and are dissolved in an organic solvent, such as methanol, and applied to the reactor surfaces and then dried. This is an expensive and cumbersome procedure, especially in large reactors. Drying is difficult and the solvent must be recovered, for economic reasons. It would be much more be more desirable to use an aqueous solution of such reaction products which did not have to be dried.